Backpack



FIG. 1 is a front perspective view of a backpack showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof;

FIG. 8 is a front view thereof with the flap shown in an open configuration; and,

FIG. 9 is a rear view thereof.

The broken lines depict portions of the backpack that form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 